Sound conduit and amplifying device.



v A. mean; SOUND GONDUIT' AND AIPLIFYING DEVICE.

,AIPLIUATIOH FILED JULY 24, 1911.

1 ,046,454; Pafiianteafi Den. 1%,; 1912.

same;

ALEX FISCHER, OF KENSINGTON, LONDON, ENGLAND.

SOUND oon'nnrr AND AMPLIFYING nnvion Specification of Letters Patent. 7 Patented Dec; 10,1912.

Application filed Ju1 24, 1911. Serial No. 640,259.

To allwhom it may concern."

Be it known that I, ALEX Fisonnn, a subject of the King of England, residing at 8 Maelise road, 'Kensington, England, have invented certain new and useful Improvements in Sound Conduits and Amplifying Devices; and I do hereby declare 'the following to be a full, clear,

and exact description of the invention, such as'will enable others skilled in the art to which it appertains to make and use the This invention relates to.sound conduits and amplifying devices and refers to that class of such conduits and amplifying devices. as are constructed with reflecting survfaces'after the manner described in my ap-v lication for Letters Patent Serial Number 555776, filed April 16, 1910, 'andmore par ticularly to those in which no sectional area at right angles to the reflector is less than the area ofthe smaller tube, or in the case of circular tubes-the vertical distance from mately "the reflecting surface tothe'inner angular where the two tubes join is approxipoint equal to the diameter of the smaller tube. I

In applying the principle of my former aforesaid patent application to certain cases, in adapting it for instance to the receivers and transmitters of telephones, to speaking tubes, as well as to sound conduits of talking machines,

certain phenomena became apparent. It was observed that when two tubes or sound conduits met at an angle and a reflector was provided, as described in the on the other hand if the reflector only of sufficient aforesaid application, if the reflector was size to include on its surface the projection of the smaller tube the sound waves were too much confined, while was of suflicient size to-include on its surface the projection of .the larger tube, the sound waves undesirable extent, and in each case the re,- sult was not so perfect as it can be made by carrying into effect the principle of my present inyention. 1

According to the present invention, in place of making the reflector of suificient size to include only the projection of the smaller tube or large enough to include that of the larger tube I make it intermediate in size. Then. supposing we have one of these tubes has a diameter of m London,

were allowedto spread out to an the tubes which areto be used as sound condu ts and 1 millimeters, while the other has a diameter of (OH-2y) mm. When these are connected together at a certain angle and .a reflector is provided the projection of the smaller.

tube on the plane of w the reflector is an ellipse with a minor axis :2 mm. in length. Aga n the projection of the larger tube on the same plane would give an ellipse with a m nor axis of (:r-l-Qy) mm.

. According to my present invention I select for the minor axis a length intermediate between the two, say (m+y) mm. This con-.

struction enables the waves vto spread to a certain extent without giving them too much freedom, and produces surprisingly good results. It will be understood that the major axis of the ellipse and the generalv dimensions of the reflecting surface are correspondingly and suitably proportioned, and the end portions of the reflector, that is the portions representing the amounts by which the reflector exceeds toward the ends the ellipse forming the projection of the smaller tube, may be adj ace n t to one of the tubes or part may be adjacent to each of these tubes. These portions may be formed ofone or more small plane reflectors set at suitable angles to catch and reflect the spreading waves, or, especially in the case of the larger tube, the auxiliary reflector may be carved in one direction sothat the spreading waves impinging at slightly varying angles, due to their having emerged from the smaller tube, may nevertheless be reflected straight along the larger tube. And in order that this invention may be better understood, 1 will now proceed to ,describe the same with reference to the drawing accompanying this specification, which shows by way of example two lllflil'lml' r carrying my invention into effect.

Figure l is a side elevation of the junction of two sound conducting tubes. Fig. 2 is a back elevation of same. is a similar view to Fig. 1 of anotl'u-r form. Fig. 4 is a '110 be equally inclined to the axis described in my application above mentioned.

It will be observed that the minor axis of the reflector c is of such size that it comes between the diameters of the smaller and larger tubes that is between :10 and (ac-t-Qy) mm. in this case about (m+3 mm. As the diameter of the larger tube is (QM-2g) mm. and the minor axis of the reflector is only a2+y it is clear that the surface of the larger tube must be curved inward somewhat in the neighborhood of the reflector in order to make a proper joint, and this may be done by cutting one or more small V-shaped pieces out of the larger tube where the joint is to be effected and bending the ends in so that a suitable joint is made with the elliptical section in the neighborhood of the minor axis, or the same result may be obtained by spinning or stamping up the metal. The reflector 0 may be carried right back so that the elliptical section is complete or it may be turned down as shown at which prevents the sound from spreading backward.

\Vhen the device is in use the sound passing up the smaller tube a after leaving such tube tends to spread outward. The size of the reflector c is calculated so as to be just suflicient to receive the impinging sound waves and to reflect them along the conduit 6 without there,being any tendency for the sound waves to be compressed at the bend.

In some cases I prefer to make the construction such that a small extra plane reflector f shown dotted at Fig. 1 is placed between the reflector c and the top of the tube 6. The object of this construction is that the waves or a portion of the waves which are proceeding up the right hand side of the tube a into the tube 7) not being confined by any walls tend to spread and therefore it is necessary to provide an extended surface for them to impinge upon which surface must be at a suitable angle for reflecting them along the tube Z2.

Referring to the modified form shown at Figs. 3 and t in this case the general construction is the same, but in place of providing a plane reflector at f, I extend the main reflector 0 so as to form a curved relecting portion h substantially as shown in the drawing.

It will be understood that I may apply the )rinciple of this invention to bends of all :inds of sound conduits, for instance to ransmitters of telephones, to megaphones, speaking tubes, ear trumpets, sound conuits of talking machines and to all classes E musical and acoustic instruments, and

that the methods of carrying out the invention may be varied to suit requirements of particular cases.

WVhat I claim as my invention and desire to secure by Letters Patent of the United States of America is 1 A sound conduit or amplifying device comprising two tubes of different cross sec tional areas meeting at an angle and a plane reflecting surface located at the junction of the tubes and equally inclined to the axes of the two tubesand in which no sectional area at right angles to the reflector is less than the area of the smaller tube, said reflecting surface being of such area that if the dimension of the small tube at right angles to the plane passing through the axes of the two tubes be a: and the corresponding dimension of the large tube be 3 then the corresponding dimension of the plane reflecting surface shall be intermediate between a: and 3 1 2. A sound conduit or amplifying device comprising two circular tubes of different diameters meeting at an angle and a plane.

reflecting surfacelocated at the junction'of the tubes and equally inclined to the axis of each tube and in which the vertical distance-' from the reflecting surface to the inner angular point where the two tu s join is approximately equal to the diameter of the smaller tube, said reflecting surface being of such areathat the minor axis of the figure formed by the reflecting surface is inter: mediate in length between the diameters of the smaller and larger tubes for the purpose set forth.

3. A sound conduit or amplifying device, comprising two tubes of different cross sectional areas meeting at an angle and a reflecting surface located at the junction of the tubes and equally inclined to the axes of the two tubesand in which no sectional area at right angles to the reflector is less than the area of the smaller tube, said reflecting surface being of such area that if the dimension of the small tube at right angles to the plane passing through the axes of the two tubes be m and the corresponding dimension of the large tube be 3 then the .corresponding dimension of the reflecting surface shall be intermediate between a: and y, said reflector having a relatively small reflecting surface set at an angle to it at that end next the larger tube.

In testimony whereof, I aflix my signa- 115 ture, in presence of two witnesses.

ALEX FISCHER.

Vitnesses LILY Snnroxns, A. E. VIDAL. 

